At present, the preparation technology of flame retardant viscose fiber mainly includes blending flame retardant modification, grafting copolymerization flame retardant modification and finishing flame retardant modification.

1, blend flame retardant modification

The blending method is to mix the additive flame retardant into the spinning stock of viscose fiber, and then spin to make the viscose fiber with flame retardant. The method also includes two ways: simple physical addition of flame retardant particles and blending of flame retardant and viscose fiber.

Physical addition method of flame retardants: flame retardants are usually phosphorous flame retardants, some also contain halogen, nitrogen or sulfur, etc., forming flame retardant synergistic effect. In order to meet the requirements of flame retardant, it is necessary to add a large number of alkali resistant, acid resistant, heat resistant and other excellent flame retardant agents in viscose, usually 10%~ 20% of the weight of the fiber, flame retardant particles in the form of "impurities" dispersed in the fiber, generally reduce the strength of viscose fiber by 10%~ 20%.

Blending two-phase regeneration technology: the main use of sol-gel technology, is generally the flame retardant precursor under certain conditions (acidic or alkaline) hydrolysis to produce active hydroxyl, and then through hydrolysis condensation reaction to form sol, in the sol stage of the flame retardant and viscose solution to form a uniform mixed system, and then through spinning into shape to make flame retardant viscose fiber.

2, graft copolymer flame retardant modification

Graft copolymerization usually involves copolymerizing macromolecular cellulose with vinyl monomers and then treating them with flame retardants. The chemical reaction between flame retardant and fiber macromolecule chain makes the reaction groups with flame retardant effect closely bind to cellulose macromolecule, and the flame retardant effect is long-lasting. However, the operation conditions of this method are relatively complex, the subsequent spinnability becomes poor, and the production cost is too high, so it has not been widely used.

3, after finishing flame retardant modification

Post-finishing flame retardant is to coat the surface of the fiber with flame retardant after the fiber is made or in the production process. The finishing agent used is usually nitrogen-containing organophosphate ester compound or antimony trioxide and halogen-containing mixed latex flame retardant. This method is simple and easy to use, but feel poor, not resistant to washing.